Language-based signaling of secondary audio

Abstract

An actual language contained within a compressed digital A / V stream within an MPEG-2 (or HDMI) stream is detected upon program transition by monitoring the actual audio content of a currently selected audio stream within the MPEG-2 (or HDMI or MP4) stream. The monitored audio stream is converted in real time to text. A frequency of sequence of three letters (a trigram) in the converted text is generated, and a plurality of the most frequent trigrams within the converted text are retained. An actual language being spoken is detected in the digital audio stream by determining a closest match between the retained plurality of trigrams and a pre-stored entry in a list of most frequent trigrams (MFT) each pre-associated with a given respective language. The detected actual language may be compared to an ISO language descriptor received in the stream, and appended to an AC-3 audio coding descriptor.

Description

BACKGROUND OF THE INVENTION1. Field of the Invention[0001]The present invention relates to reliable and accurate signaling of a secondary audio channel received by a set-top box or HDMI sink device such as a television or DVR.2. Background of Related Art[0002]Digital TV is transmitted as a stream of MPEG-2 data known as a transport stream. Each transport stream has a data rate of up to 40 mb / s for a cable or satellite network, which is enough for seven or eight separate TV channels, or about 25 mb / s for a terrestrial network.[0003]Each transport stream includes a multiplexed set of sub-streams known as elementary streams. Each elementary stream can contain MPEG-2 encoded audio, MPEG-2 encoded video, or data encapsulated in an MPEG-2 stream. Each elementary stream has a unique 13-bit ‘packet identifier’ (PID) that identifies that stream within the transport system.[0004]Each MPEG-2 elementary stream is packetized into a packetized elementary stream (PES). Each packetized elementary s...

AI Technical Summary

Benefits of technology

The present invention provides a method for detecting actual languages in digital audio streams, such as in MPEG-2 or HDMI streams. This is by monitoring the content of the audio stream and converting it to text in real-time. The method includes identifying a sequence of three letters (a trigram) in the converted text and retaining a list of the most frequent trigrams associated with various languages. By comparing the retained trigrams with a set of pre-stored entries, the method can detect the actual language being spoken in the audio stream. This technology can be applied in various areas such as language identification in voice-controlled systems or media content analysis.

Problems solved by technology

However, as the inventors hereof appreciated, this automatic switching of played audio back to a main audio elementary stream can occur upon events such as channel transitions (a change of channel), a change of program from one program to the next (e.g., at the top of the hour, etc.) Or the selected audio channel may change for other reasons, which the present inventors have appreciated may be confusing or distracting to the viewer of the HDMI sink device, e.g., a television 902.

Adding to the confusion is that a broadcaster may signal an audio elementary stream as generically containing “original audio” language, without specifying the exact language being used, thus making automatic selection of the proper audio channel unreliable at best, or at worst not always possible.

As explained above, the inventors have appreciated that use of the ISO language descriptor for automatic selection of audio channel is unreliable at best, and not always possible at worst.

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